Computer Aided Process Planning Research Articles

Development of CIM Applications from PDES/STEP Information Models

This paper defines the problems associated with Information storage, and transfer, in the creation of applications within the computer-aided engineering sphere. The PDES/STEP information modelling environment is proposed as a possible means to solve the lack of consistent product information that abounds in this area. The paper also supports the creation of a manufacturing model using the EXPRESS language that will allow manufacturing decisions to be based on current resource availability. This support is shown by the development of a simple manufacturing model to define a machine resource. The need for, and types of, other resources within this model are also explained. The application under investigation is computer-aided process planning. A description of the possible environment of a CAPP application is provided, along with the inclusion of form features as a means of simplifying the planning process. The paper also proposes to use the information structures so created in the development of a generic query language, utilizing C++, an X-window-based toolkit, and the use of EXPRESS-G type structures, that will allow non-stop PDES/STEP users to access and query data files, and so create computer- integrated manufacturing applications more easily than currently possible.

Feature Recognition in Computer-Integrated Manufacturing

To integrate CA* systems like computer-aided design (CAD), computer-aided manufacturing (CAM), or computer-aided process planning (CAPP) with other applications in the world of computer-integrated manufacturing (ClM), one principal approach currently

A blackboard-based process planning system for the surface mount manufacture of PCBs

This paper describes a real-time computer-aided process planning (CAPP) system for printed circuit board (PCB) assembly using surface mount technology. The prototype, dynamic, realtime CAPP system described uses a blackboard to integrate multiple knowledge sources (knowledge bases) in implementing the process planning procedure. The CAPP system is implemented using the expert system environment (ESE) and structured query language (SQL). The system uses two subsystems (knowledge bases). They are a planning subsystem which performs the static process planning task and a dynamic information processing subsystem which considers the real-time changes on the shop floor and routes the PCB assembly flow. The integrated system developed generates process plans that can be implemented in real time. The use of the blackboard concept for CAPP architecture is unique and well suited for this task.

The generation of bending sequences in a CAPP system for sheet-metal components

An important process-planning task in sheet-metal manufacturing is the determination of bending sequences for individual components. Computer-aided generation of these sequences, as part of a computer-aided process-planning (CAPP) system, can relieve the workload of process-planning departments, this being especially important in small batch manufacturing environments. This paper discusses the functions that have to be performed during the determination of bending sequences, focusing on accuracy aspects. The generation of bending sequences is also put into the broader perspective of an integrated CAPP system such as PART-S, which is under development presently in the author's laboratory.

A Formal Approach to Integrating Computer-Aided Process Planning and Shop Floor Control

A formal approach for integrating Computer-Aided Design (CAD), Computer-Aided Process Planning (CAPP), and shop floor control for rotational components is presented in this paper. It is assumed that this approach will be implemented within the framework of a three level hierarchical CIM architecture that consists of the following levels in the hierarchy: shop floor, workstation and equipment (Joshi et al., 1991). Our approach to CAPP consists of machining feature identification, definition, classification, representation, and reasoning, provided through a CAD model of a product. Geometric entities are identified from a Drawing Exchange Format (DXF) file. The identified entities form the basis for the construction of primitive manufacturing features. The primitive features are assembled together based upon the precedence among features, into a graph, called a feature graph. However, the primitive features may or may not be manufacturable in terms of depth of cut, tool geometry, surface finish, and material handling required. Hence it is necessary to convert the feature graph into a manufacturing task graph, which consists of specifications of alternative functional tasks that are manufacturable. The task graph may be converted into a hierarchical set of process plans, based on the planning criteria at each level in the control hierachy, to reflect the processing requirements at each level. The shop planning function decomposes the task graph into a set of workstation level plans. Each workstation level plan is aggregated into a set of equipment level process plans by the workstation planning function. The equipment level plan is converted into a unique task sequence by the equipment planning function. This sequence is then executed according to specifications by the equipment level execution function. Provision of alternative routes in process plans provides for flexible means of on-line planning and control.

Manufacturing Cost Analysis of Surface Mount PCB Designs

A product's design influences its manufacturing process and the associated costs. Consequently, design engineers need to review their designs from a manufacturing perspective. While ‘Design For Manufacturing’ (DFM) tools often identify the manufacturing problems associated with a design, they would be more effective if these problems could be represented to the designer in terms of a cost value. This research developed a cost estimation tool for the designer in the surface mount printed circuit board (PCB) domain by integrating computer aided design, computer aided process planning (CAPP) and cost estimation techniques using a knowledge based framework. The cost estimation can be done in two design stages. First, an initial approximation of the manufacturing cost can be obtained using information such as the component mix, type of substrate and the size of board. After the detailed design of the PCB has been developed, a more accurate PCB assembly cost can be obtained using computer aided design (CAD) data. Both cost determination strategies would require the generation of a macro‐process plan. The cost advisor considers tangible and intangible factors. This cost advisor and the DFM environment have been developed using C ++ and object oriented programming constructs under the MS Windows operating system.

Cost based surface mount PCB design evaluation

In today's manufacturing field there is continuous demand for product flexibility and shorter product throughput time. Production planning and cost estimating activities need to be speeded up. Consequently, the traditional gap between the designer who designs new products and the estimator who evaluates the financial consequences of the design is fading. Cost optimization is being integrated in the design process, and the designer needs to take more responsibility for the cost of the product at the design stage itself. There is a lack of tools to assist the designer in analyzing a Printed Circuit Board's (PCBs) design from a manufacturing perspective, especially from an economic aspect. This is true in Surface Mount Technology (SMT) production where the integration of the design and manufacturing functions is often hampered by the lack of sufficient, in-depth manufacturing knowledge and associated cost information. This research developed a cost estimation tool for the designer in the surface mount PCB assembly domain by integrating Computer Aided Design (CAD), Computer Aided Process Planning (CAPP), and cost estimation techniques using a knowledge based framework. Cost estimation can be done at two design stages. First, a rough cost estimate can be obtained from knowing the component mix, the type of boad material, and the size of board. Then, after the detailed design, a more accurate assembly cost can be obtained by generating a macro-process plan from the given CAD data. The cost module considers tangible factors including the material costs, the equipment costs, process costs, and the labor costs. The model used also considers the intangible cost in a preliminary evaluation of design costs. The cost advisor and the Design For Manufacture (DFM) environment have been developed using C++ and object oriented programming constructs under the MS Windows operating system.

Using Hierarchical Constraint Satisfaction for Lathe-Tool Selection in a Computer-Integrated Manufacturing Environment

We discuss how to treat the automatic selection of appropriate lathe tools in a computer-aided process planning (CAPP) application as a constraint satisfaction problem (CSP) over hierarchically structured finite domains. Conceptually, it is straightf

A COST BASED SYSTEM FOR CONCURRENT PART AND PROCESS DESIGN

ABSTRACT This paper presents a Real Tune Computer Aided Process Planning (RTCAPP) system which can serve as a support tool for economic decision making during design activities. The system is capable of providing the information about manufacturing implication of each added design feature to the designer during the design process of prismatic parts. A knowledge-based system using a bierarchical planning scheme and a multi-bank rule base is developed to generate near-optimal process plans in real time. The planning process is supported by an optimization module which uses dynamic programming to minimize manufacturing costs. The incremental planning mechanism utilizes as much of the existing plan information as is necessary to generate a new process plan, whenever the design is updated. The system serves as an effective concurrent engineering tool that can be used to provide real time feedback on the manufacturing cost consequences to the designer

RDCAPP: A real-time dynamic CAPP system for an FMS

Computer-aided process planning (CAPP) systems need to consider the uncertain nature of the shop-floor prior to the identification of job routes and processing sequences. This paper describes the design and development of a prototype, real-time dynamic CAPP (RDCAPP) system for a multimachining-centre flexible manufacturing system (FMS). Concepts relevant to this research include CAPP, profile input using group technology (GT), artificial-intelligence-based expert systems, and FMSs.

An integrated fixture planning and analysis system for machining processes

Fixture planning is an important part of computer-aided process planning (CAPP), which is the link between design and manufacturing in a CIM environment. This paper presents a rational approach to computer-assisted fixture planning (CAFP), emphasizing integration of fixture planning with process planning, an issue that has not been adequately addressed until very recently. A systematic approach to fixture selection is outlined for planning of modular fixtures. A prototype CAPP-CAFP system has been developed at UCLA and linked to a commercial CAD system, namely, CADAM. Part design information can be extracted from the CAD model and multiple-view engineering drawings of a part stored in the CADAM system. Modular fixture elements can be selected automatically by the CAPP-CAFP system and the generated fixture layout can be displayed on the screen. Included also in the system is a fixture analysis module for verification and rationalization of a fixturing scheme. The force analysis module has a built-in local optimization routine that can determine the clamping forces of more reasonable magnitudes. The friction forces between the fixture and the workpiece can also be considered for simple cases.

A Review of: “Computer-Aided Process Planning.” By HSU-PIN WANG and JIA-KANG LI (Elsevier, 1991 [Pp. 400] Price: US$134.50, Dfl 23500.

A Review of: “<i>Computer-Aided Process Planning.</i>” By HSU-PIN WANG and JIA-KANG LI (Elsevier, 1991 [Pp. 400] Price: US$134.50, Dfl 23500.

An expert process planning system for electronics PCB assembly

The electronics manufacturing is one of the most prosperous industries in the world today. With the continuous advancement in electronics components and automatic assembly machines, printed circuit board (PCB) assembly has become more dynamic and complicated. The process planning is usually a complex and time-consuming task yet an important key in accomplishing a fully automated computer integrated manufacturing (CIM) system. The added diversity of electronic products, inefficiency in planning time and inconsistency among manually generated process plans have increased the necessity for developing a computer aided process planning (CAPP) system for electronics assembly. The success of surface mount technology (SMT) and flexible manufacturing concept make the process planning for electronics assembly a more frequent and challenging task than ever before. This paper discusses and presents a prototype Expert Process Planning System for Electronics Assembly (EPPSEA) which utilizes the expert system technique to solve the complicated process planning problem in a PCB assembly system. The structure, generating strategy and application of the system are described.

Evolution and Future Perspectives of CAPP

Modern manufacturing is characterized by low volume, high variety production and close tolerance high quality products. Computer Integrated Manufacturing (CIM) is recognized as an effective platform for increasing manufacturing competitiveness. Computer Aided Process Planning is an essential key for achieving CIM. The integration of design, computer aided process planning (CAPP) and production planning and control (PPC) is becoming essential especially in a concurrent engineering environment where many product life cycle factors are of concern. An overview of the major development thrust in CAPP is presented along with some of the evolving trends and challenges such as rapid, generic, dynamic and/or distributed process planning. Related issued of quality and evolving standards are also discussed.

Computer-aided process planning—State of the art and future development

Computer-aided process planning (CAPP) is regarded as the critical link between design and manufacturing. Particularly in the integration of computer-aided manufacturing, process planning plays an outstanding role in the integrated flow of information. This paper gives a broad view of today's situation in computer-aided process planning in a real industrial environment. Characteristics for the classification of CAPP systems are derived and the main trends in the future development of CAPP software are pointed out. Feature-based modelling of manufacturing processes as the basis for integration-oriented software development is briefly described.

An operations network generator for computer aided process planning

Computer aided process planning (CAPP) is an important interface between computer aided design (CAD) and computer aided manufacturing (CAM) in the computer integrated manufacturing (CIM) environment. A preliminary planning module developed as a part of a whole CAPP system is described in this paper. The preliminary planning deals with sequencing at the form-feature level. Processing of form feature involves certain degree of abstraction, as it is done independent of the shop-floor resources. Firstly, various feasible sequences are generated from the feature precedence relation based on the precedence and geometric tolerance constraints using an intelligent search strategy. In the next step, optimal/near-optimal sequences are generated using a genetic algorithm (GA) which prunes the initial feasible sequences using multiple optimality criteria with respect to feature adjacency, datum/reference features and preference in processing the features.

High-level planning and control: An IDEF analysis for airframe manufacture

Computer utilization in manufacturing systems is increasing at a rapid rate. Developments thus far have been disjointed. Much work needs to be done in the area of integrating computer aided design and computer aided manufacturing (CAD/CAM). Tolerance control is an important component in the integration of CAD and CAM. Selection of design tolerances affects the build-ability of a product. The selection of manufacturing processes and sequence of processes affects process tolerance stacking. Unexamined process tolerance stacking leads to scrap and rework. A computer aided tolerance control (CATC) system is presented in this paper. This system is based on the tolerance chart technique. The CATC system is interactive and uses computer graphics for information display. The system can be used for computer aided process planning (CAPP) and for CAD/CAM integration.

A PDES/ STEP-based product data preparation procedure for computer-aided process planning

This paper is focused on a procedure for preparation of product data for computer-aided process planning. The foundation of the project is a set of emerging standards, known as PDES/ STEP. It is realized that, in order to develop a procedure for consistent, unambiguous data abstraction from a generic data structure, the foundation on which the procedure is based is crucial. It is believed that PDES/ STEP, although not fully developed, will be able to meet those requirements. The product data preparation procedure is built upon a concept called application protocol. An application protocol is specific to an engineering application, in this case computer-aided process planning. The reason for adopting such a concept is explained in the paper. Other important elements to this project include EXPRESS, C++ and R OSE database, which all are explained in the paper with examples. The paper is concluded with plans for further research.

An Opportunistic Approach to Process Planning within a Concurrent Engineering Environment

Summary Traditionally, design and manufacturing activities have been serially linked by the process planning function. One objective of concurrent engineering is to transform this sequential approach into a more interactive, parallel process. To support concurrent engineering, computer-aided process planning (CAPP) systems must be developed that supports an opportunistic style of process planning. This paper presents XTURN, a CAPP system implemented within the IDEEA environment that Supports a flexible and opportunistic style of process planning. XTURN enables engineers to explore alternative process plans in early design stages. The engineer controls process selection strategies, while XTURN determines the interactions between the various choices, flags those that arc inconsistent, and offers advice on resolving any inconsistencies. XTURN does not require that an inconsistency be immediately removed, rather it remembers the inconsisitency and allows the engineer to continue exploration. This paper describes he development and application of XTURN and IDEEA. Also, ongoing research that extends IDEEA into a fully distributed system integration workbench to support concurrent engineering is discussed.

A real-time computer-aided process planning system as a support tool for economic product design

Abstract A new computer-aided process planning (CAPP) system is presented that serves as a tool for concurrent design of prismatic parts and their manufacturing processes. The system provides timely manufacturing cost feedback to the designer for each added design feature. A hierarchical planning technique, an expert system with a multibank rule base, and a dynamic programming-based optimization module are employed in this real-time process planning system.